Recently, as the world entered the information age, display apparatus for processing and displaying a large amount of information have been rapidly developed. Accordingly, various display apparatus have been developed and have attracted a lot of attention.
Specific examples of the display apparatus may include a liquid crystal display apparatus (LCD), a plasma display panel apparatus (PDP), a field emission display apparatus (FED), an electroluminescence display apparatus (ELD), and organic light emitting diodes (OLED). These display apparatus generally have excellent properties of a thin profile, light weight and low power consumption and thus their application fields have been increased continuously. In particular, in most of electronic apparatus or mobile apparatus, the display apparatus has been used as one of a user interface.
Also, studies of transparent display apparatus through which a user may see objects or images located on the opposite side are being actively conducted.
The transparent display apparatus may have advantages of better use of space, interior and design, and may have various application fields. The transparent display apparatus may solve spatial and temporal restrictions of electronic apparatus as compared with conventional display apparatus by implementing a display apparatus with functions of information recognition, information processing and information display as a transparent electronic apparatus. Such transparent display apparatus may be used for a smart window, which may be used as a window of a smart home or a smart car.
Particularly, an LCD may be implemented as a transparent display apparatus by applying an edge type backlight thereto, but a transparent display apparatus based on LCD has a problem in that a transmittance ratio is very low and transparency is decreased by a polarizing plate used for implementation of black and also has a problem with outdoor visibility.
Further, a transparent display apparatus based on OLED has higher power consumption than the transparent display apparatus based on LCD and has difficulty in displaying a true black. Also, the transparent display apparatus based on OLED has no problem with a contrast ratio under a dark environment, but has a disadvantage of reduction in a contrast ratio in a normal environment with light.
Therefore, in order to implement a transparent mode and a light shielding mode, there has been suggested a method for utilizing a polymer dispersed liquid crystal (PDLC) and a polymer networked liquid crystal (PNLC) for a light control apparatus of the transparent display apparatus based on OLED. The polymer dispersed liquid crystal (PDLC) or the polymer networked liquid crystal (PNLC) may be formed by mixing a monomer with a liquid crystal and then irradiating ultraviolet (UV) rays thereto.
Particularly, the polymer dispersed liquid crystal (PDLC) has a structure in which a liquid crystal is formed within a droplet, and the polymer networked liquid crystal (PNLC) has a structure in which a polymer is distributed in a network structure on a liquid crystal.
If an electric field is applied to the polymer dispersed liquid crystal (PDLC) or polymer networked liquid crystal (PNLC), an alignment of the liquid crystal is changed, and, thus, light incident from the outside can be scattered or transmitted. That is, a apparatus using the polymer dispersed liquid crystal (PDLC) or polymer networked liquid crystal (PNLC) can scatter or transmit light without a polarizing plate, and, thus, can be used as a light control apparatus of a transparent display apparatus.